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Relative importance

Environmental stress model. stress amelioration. competition. predation. diversity of basal species. Relative importance. associational defenses. Environmental stress. Bruno, Stachowicz & Bertness (2003). Richness of primary space holders

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Relative importance

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  1. Environmental stress model stress amelioration competition predation diversity of basal species Relative importance associational defenses Environmental stress Bruno, Stachowicz & Bertness (2003)

  2. Richness of primary space holders Richness of secondary space holders (sessile and mobile associated species) Overall richness Scrosati & Heaven (2007, Marine Ecology Progress Series 342: 1-14) Bruno, Stachowicz & Bertness (2003, Trends in Ecology and Evolution 18: 119-125)

  3. Scrosati & Heaven (2007) in Atlantic Canada Vertical gradient Desiccation - Temperature Irradiance - Osmotic potential Horizontal gradient Wave exposure - Ice scour

  4. - Gulf of St. Lawrence coast - Atlantic coast Nova Scotia Nova Scotia New England

  5. Methods Environmental stress gradients Vertical gradient (3 levels) High - Mid - Low intertidal Upper limit determined using barnacles Horizontal gradient (2-3 levels) Gulf (wave + ice): Sheltered - Exposed Atlantic (wave): Sheltered - Intermediate - Exposed dynamometers (wave exposure) cages (ice scour)

  6. Methods Richness, Diversity & Evenness • Summer • Abundance of all seaweeds and invertebrates (% cover) • 25 cm x 25 cm quadrats (n = 20 per Elevation x Exposure combination) RichnessSr of species Diversity (Simpson's index) 1 - D = 1 -  (pi) Evenness (Simpson's index)E = (D * S)-1

  7. Results 38 seaweeds - 29 invertebrates

  8. Results - Richness across Elevation Means ± SE Gulf of St. Lawrence 2 = 39 % Elevation Atlantic 2 = 41 % Elevation

  9. Results - Richness across Exposure Means ± SE Gulf of St. Lawrence 2 = 10 % Wave - Ice Exposure Atlantic 2 = 12 % Wave Exposure

  10. Environmental stress model (ESM) Predation Hypothesis Intermediate Disturbance Hypothesis RICHNESS SESSILE SPECIES (PRIMARY SPACE HOLDERS) Menge & Sutherland (1987, American Naturalist 130: 730-757)

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